Biofuels: The Devil in the Details

www.biosciencemag.org April 2010 / Vol. 60 No. 4 • BioScience

Letters

In a recent Viewpoint on biofuels (BioScience 59: 926–927), Tom Simp-son addressed important shortcom-ings of corn ethanol production: low net energy gain, competition with food production, and the loss of nitrogen from fertilizers and its en-vironmental consequences. Simpson proposed an agricultural landscape that could produce food, feed, and fuel while improving water, air, and habitat quality by relying more on perennial biomass. However, other environmental problems are related not only to ethanol production but also apply to production of perennial biomass.

To call anything a sustainable bio-fuel strategy requires specifying a time frame. If the chosen time frame is short enough, anything becomes sus-tainable and degenerates to an oxymo-ron (Flueck and Smith-Flueck 2006). Generally accepted sources put US reserves of easily mined phosphorus deposits as sufficient to last for another 25 years at current application levels. Corn grain harvest, though, removes about 7.2 kilograms (kg) of phospho-rus (P, expressed as P₂O₅) per metric ton of corn grain, and 1.64 kg per metric ton of corn silage. Any crop will, however, remove P and thus ne-cessitate replacement.

Twenty-five years is a mere blink of time. China, having a major deposit of easily accessible P deposits, has very recently taken measures to prevent P leaving China, for obvious reasons. Since the year 2000, P prices have in-creased several-fold, and “peak phos-phorus” is commonly mentioned.

Another consequence of biomass export is soil acidification, which re-quires corresponding countermeasures such as liming. As inputs necessary

Flueck WT, Smith-Flueck JM. 2006. Herbicides and forest biodiversity: An alternative perspec-tive. Wildlife Society Bulletin 34: 1472–1478. doi:10.1525/bio.2010.60.4.17

Response from Simpson

I appreciate Werner Flueck’s comments and generally agree with the opening concern and ending statement, but have a different perspective on much of what lies between the two. “Peak phosphorus” (P) is real and should be a general con-cern, not just with biofuels. However, many of the biomass uses I discussed, such as gasification or pyrolysis, concen-trate the P in char or ash, thus facilitat-ing recyclfacilitat-ing. Further, many soils in the United States and elsewhere have exces-sive P levels from long-term manure application. Biomass production may allow “mining” and recycling of excess P without affecting crop yields while improving water quality.

Flueck refers to high pesticide use and declining yields in a “few years” with switchgrass, which is counter to my knowledge. Pesticide use is primar-ily at establishment, and even then, may not be what is needed annually to grow corn. Most research I have seen indi-cates about a 20-year productive life span for a switchgrass stand. Improved seeds and seeding methods are reduc-ing time of establishment to one year. I agree with his conclusion that biofuels, of all kinds, should be an interim solu-tion to liquid energy security, so criti-cal, productive land resources can be returned to food production.

TOM SIMPSON Tom Simpson (toms@ waterstewardshipinc.org) is the president and executive director of Water Stewardship, Inc., in Annapolis, Maryland.

doi:10.1525/bio.2010.60.4.18

for biofuel production are becoming scarcer, their further production in itself will require more external energy (as with P), or compete with easy en-ergy sources (natural gas for nitrogen fertilizer). If corn ethanol production does not pass the sustainability test regarding the environment according to Simpson, I posit that neither can perennial biomass pass the test.

Switchgrass removes about 4.55 kg of P per metric ton, and because it leads to higher biomass export than corn grain, it also results in greater P loss. Moreover, others have pointed out that it requires much more pes-ticide than corn, and considering the initial two years of no harvest and declining yields after a few years, corn yields outperform switchgrass by a factor of 2 or more.

Overall, it is not appropriate to label biofuels as sustainable alternatives, as if we can get something for nothing (i.e., as if it involves only solar energy conversion). Given the mentioned constraints, in addition to several oth-ers (Flueck and Smith-Flueck 2006, Flueck 2009), it would be more precise to label biofuels as temporary solu-tions to give us time to rethink the cur-rent level of dependence on energy.

WERNER FLUECK Werner Flueck (wtf@deerlab. org) is with the National Council for Scientific Research, Argentina Institute of Natural Resources Analysis at the Universidad Atlantida Argentina, and the Swiss Tropical Institute, University of Basel. References cited

Flueck WT. 2009. Evolution of forest systems: The role of biogeochemical cycles in deter-mining sustainable forestry practices. Ecol-ogy and Society 14: r4. (18 February 2010;